Roof Pitch Calculator

Last updated: 05 Sep 2026 | Author: Brij | Review By: Irshad

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Use our free Roof Pitch Calculator to calculate rafter length, roof pitch in x:12 ratio, degrees, and percentage from the rise and run of a roof.

Enter Rise and Run

Rise:

Run:

Result:

Rafter Length:

Roof Pitch (x:12):

Roof Pitch (Degree):

Roof Pitch (%)

What is Roof Pitch?

Roof pitch describes the steepness of a roof and is commonly expressed as a ratio such as 4:12, in degrees, or as a percentage. A 4:12 roof pitch means the roof rises 4 inches for every 12 inches of horizontal run.

The Roof Pitch Calculator uses the roof's rise and run to calculate the rafter length, roof pitch in x:12 ratio, roof pitch in degrees, and roof pitch as a percentage. Enter the rise and run in inches, feet, centimeters, or meters to quickly determine the roof slope and related measurements.

Key Formulas for Roof Pitch Calculations

1. Calculate Rafter Length

The rafter length is the hypotenuse of the right triangle formed by the roof's rise and run. Using the Pythagorean theorem:

$\text{Rafter Length} = \sqrt{\text{Run}^2 + \text{Rise}^2}$

Where:

$\text{Run}$ = Horizontal distance (in feet or inches)
$\text{Rise}$ = Vertical height (in feet or inches)

2. Roof Pitch (x:12)

Roof pitch as x:12 expresses the slope of the roof as a ratio where the run is standardized to 12 units.

$\text{Roof Pitch (x:12)} = \frac{\text{Rise}}{\text{Run}} \times 12$

Where:

$\text{Rise}$ = Vertical height of the roof
$\text{Run}$ = Horizontal distance of the roof

3. Roof Pitch (Degrees)

To calculate the roof pitch in degrees, use the arctangent function:

$\text{Roof Pitch (Degrees)} = \arctan\left(\frac{\text{Rise}}{\text{Run}}\right)$

Where:

$⁡\arctan$ = Inverse tangent function

4. Roof Pitch (%)

The slope of the roof as a percentage is calculated by dividing the rise by the run and multiplying by 100:

$\text{Roof Pitch (\%)} = \left(\frac{\text{Rise}}{\text{Run}}\right) \times 100$

Where:

$\text{Rise}$ = Vertical height of the roof
$\text{Run}$ = Horizontal distance of the roof

Example Calculation

Given:

Run = 10 ft
Rise = 6 ft

1. Rafter Length:

Using the formula:

$\text{Rafter Length} = \sqrt{10^2 + 6^2}$

$\text{Rafter Length} = \sqrt{100 + 36}$

$\text{Rafter Length} = \sqrt{136} \approx 11.66 \, \text{ft}$

2. Roof Pitch (x:12):

Using the formula:

$\text{Roof Pitch (x:12)} = \frac{6}{10} \times 12$

$\text{Roof Pitch (x:12)} = 0.6 \times 12 = 7.2$

3. Roof Pitch (Degrees):

Using the formula:

$\text{Roof Pitch (Degrees)} = \arctan\left(\frac{6}{10}\right)$

$\text{Roof Pitch (Degrees)} = \arctan(0.6) \approx 30.96^\circ$

4. Roof Pitch (%):

Using the formula:

$\text{Roof Pitch (\%)} = \left(\frac{6}{10}\right) \times 100$

$\text{Roof Pitch (\%)} = 0.6 \times 100 = 60\%$

Final Results:

For a roof with a run of 10 ft and a rise of 6 ft:

Rafter Length: 11.66 ft
Roof Pitch (x:12): 7.2:12
Roof Pitch (Degrees): $30.96^\circ$
Roof Pitch (%): $60\%$

FAQs

1. What is a 2/12 roof pitch?

A 2:12 roof pitch means the roof rises 2 inches for every 12 inches of horizontal run. It is considered a relatively low roof slope compared with steeper pitches.

2. How do I calculate roof pitch?

Roof pitch is calculated by comparing the vertical rise to the horizontal run. The pitch ratio can be converted to an x:12 format by multiplying the rise-to-run ratio by 12.

For example, a roof with a 6-inch rise and a 12-inch run has a 6:12 roof pitch.

3. What does a 6/12 roof pitch mean?

A 6:12 roof pitch means the roof rises 6 inches for every 12 inches of horizontal run. It corresponds to a roof angle of approximately 26.6 degrees and a slope of 50%.

4. How do I convert roof pitch to degrees?

To convert roof pitch to degrees, use the inverse tangent of the rise divided by the run:

Angle = arctan(rise ÷ run)

For example, a 6:12 roof pitch has an angle of approximately 26.6°.

5. What is the difference between roof pitch and roof slope?

Roof pitch and roof slope both describe how steep a roof is, but they are commonly expressed differently. Roof pitch is often written as a ratio such as 6:12, while roof slope may also be expressed as a percentage or ratio.

6. How is rafter length calculated from rise and run?

Rafter length is the sloped distance between the rise and run of the roof's right triangle. It can be calculated using the Pythagorean theorem, with the rise and run as the two perpendicular sides.

The Roof Pitch Calculator calculates the rafter length automatically from the rise and run you enter.

7. Can I calculate roof pitch in different units?

Yes. The calculator allows you to enter both rise and run in inches, feet, centimeters, or meters. The calculator uses the entered measurements to determine the roof pitch and rafter length.

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